Weathering and erosion of limestone by soil indigenous moulds-a case study of Aspergillus niger
The natural weathering and erosion of minerals of limestone is a common problem.Especially,the representative biological weathering by the soil mold played important roles in the change of structures and properties of minerals and the regulation of soil nutrient environment.In order to reveal the mechanism of weathering and erosion of minerals of limestone by soil resident molds,we have studied the growth characteristics of Aspergillus niger and its metabolites,and the release behavior of Ca2+from limestone by the action of Aspergillus niger,,have made comparative study on the characteristics of dissolution behavior of limestone by oxalic acid,and have explored the mechanism of weathering and erosion of limestone by Aspergillus niger.The results show that Aspergillus niger has relatively high acid-producing capability.The main organic acids produced by Aspergillus niger include oxalic acid,malic acid,citric acid,acetic acid and succinic acid.These organic acids can reduce the pH value of the medium to about 2.5.Alkaline environment can promote the growth of Aspergillus niger in a certain extent.The weathering and erosion effect of limestone by oxalic acid is much smaller than that by Aspergillus niger under the same condition.There are mainly two ways of the weathering and erosion of limestone by Aspergillus niger including the disoolution of limestone by its secreted acidic metabolites and the mechanical damage caused by the wrapping and drilling limestone particles by its hyphae.The results of this study can provide a theoretical basis for the involvement of microoreganisms in the karsting process and the biological control of rocky desertification in the natural environment.
limestoneweathering and erosionAspergillus nigerOrganic acids
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